The present invention relates to an impeller, and more particularly to one for a motorboat.
A motorboat normally includes a propeller shaft having a transmitting end having a plurality of spaced axial splines, a nozzle rotatably mounting therein a hollow fixing shaft driven by the propeller shaft projecting into the nozzle, and an impeller having a hollow shaft member having a leading end, a trailing end and an inner thread screwing thereto an outer thread of the fixing shaft having a plurality of inner grooves respectively engaging therein the splines. Alternatively, it can be designed that the impeller has the hollow shaft member thereof provided with a plurality of inner grooves capable of respectively engaging therein the splines by the propeller shaft. The present invention deals with the impeller of the first type having an inner thread.
As shown in FIGS. 1 & 2, the prior impeller 10 includes a hollow shaft member 11 having an inner thread 12 and crosssectionally hexagonal leading end 13 suffers from the following disadvantages:
1) Since leading end 13 is crosssectionally hexagonal, it will result in a turbulent flow in the water, and a cavitation on the impeller 10 so that the vibration phenomenon will be incurred on the impeller 10 and the motorboat. PA1 2) Upon disassembling impeller 10 from the motorboat, the housing 15 for nozzle 17 must first be detached from the motorboat in order that a spanner can engage with leading end 13 to screw impeller 10 off hollow fixing shaft 16. In addition, leading end 13 is tapered so that the spanner cannot securely engage with leading end 13 and the engaging surfaces of the spanner and/or leading end 13 may easily get damaged. Thus, the disassembling procedure of impeller 10 is troublesome and relatively uneasy.